<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>Life cycle callbacks test</title>
    <style>
        custom-square {
            margin: 20px;
        }

        div {
            border: 1px solid #ccc !important;
        }
    </style>
    <script defer src="main.js"></script>
</head>
<body>
<h1>Life cycle callbacks test</h1>
<ul is="custom-square"></ul>
<div>
    <button class="add">Add custom-square to DOM</button>
    <button class="update">Update attributes</button>
    <button class="remove">Remove custom-square from DOM</button>
</div>

</body>
</html>